Ball injecting apparatus for wellbore operations

ABSTRACT

Apparatus is provided injecting drop balls into a wellbore, such as for actuating downhole tools. A ball magazine adapted for storing drop balls, in two or more transverse ball chambers, is axially movable in a magazine housing mounted at a transverse port to a fluid passage in fluid communication with the wellbore. The magazine is serially actuable for aligning a first and subsequent chambers with the transverse port for injecting stored balls to the wellbore. An indicator, such as a rod extending from the magazine housing, can be used to indicate the relative location of the chamber and transverse port. The apparatus can be used in a system and methodology for actuating two or more downhole tools spaced at intervals along the wellbore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a regular application claiming priority of U.S. Provisional Patent application Ser. No. 60/895,350, filed on Mar. 16, 2007, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to apparatus and method for injecting balls into a wellbore, such as drop balls, frac balls, packer balls and other balls for interacting with downhole tools or for blocking perforations in casing in the wellbore. More particularly, the apparatus and method uses an actuator and ball magazine for controllably releasing balls into a fluid stream which is pumped into the wellbore.

BACKGROUND OF THE INVENTION

It is known to conduct fracturing or other stimulation procedures in a wellbore by isolating zones in the wellbore using packers and the like and subjecting the isolated zone to treatment fluids at treatment pressures. In a typical fracturing procedure, for example, the casing of the well is perforated to admit oil and/or gas into the well and fracturing fluid is then pumped into the well and through the perforations into the formation. Such treatment opens and/or enlarges draining channels in the formation, enhancing the producing ability of the well.

It is typically desired to stimulate multiple zones in a single stimulation treatment, typically using onsite stimulation fluid pumping equipment. A series of packers in a packer arrangement is inserted into the wellbore, each of the packers located at intervals for isolating one zone from an adjacent zone. It is known to introduce a drop ball through the wellbore to selectively engage one of the packers in order to block fluid flow therethrough permitting creation of an isolated zone uphole from the packer for subsequent treatment or stimulation. Once the isolated zone has been stimulated, a subsequent drop ball is dropped to block off a subsequent packer, uphole of the previously blocked packer, for isolation and stimulation thereabove. The process is continued until all the desired zones have been stimulated. Typically the balls range in diameter from a smallest ball, suitable to block the most downhole packer, to the largest diameter, suitable for blocking the most uphole packer.

At surface, the wellbore is fit with a wellhead including valves and a block, such as a frachead, which provides fluid connections for introducing stimulation fluids including sand, gels and acid treatments into the wellbore. Conventionally, operators manually introduce drop balls to the wellbore through an auxiliary line, coupled through a valve, to the wellhead. The auxiliary line is fit with a valved tee or T-configuration connecting the wellhead to a fluid pumping source and to a ball introduction valve. The operator closes off the valve at the wellhead to the auxiliary line, introduces one drop ball and blocks the valved T-configuration. The pumping source is pressurized to the auxiliary line and the wellhead valve is opened to introduce the ball. This procedure is repeated manually, one at a time, for each ball. This operation requires personnel to work in close proximity to the treatment lines through which fluid and balls are pumped at high pressures and rates. The treatment fluid is energized which is highly dangerous.

Aside from being a generally dangerous practice, other operational problems have occurred, such as valves malfunctioning and balls becoming stuck and not being pumped downhole. These problems have resulted in failed well treatment operations, requiring re-working which is very costly and inefficient. At times re-working of a well formation following an unsuccessful stimulation treatment may not be successful, which results in production loss.

Other alternative methods and apparatus for the introduction of the drop balls have included an array of remote valves positioned onto a multi-port connection at the wellhead with a single ball positioned behind each valve. Each valve requires a separate manifold fluid pumper line and precise coordination both to ensure the ball is deployed and to ensure each ball is deployed at the right time in the sequence, throughout the stimulation operation. The multi-port arrangement, although workable, has proven to be very costly and inefficient. Further, this arrangement is dangerous to personnel due to the multiplicity of lines under high pressure connected to the top the wellhead during the stimulation operation. It is known to feed a plurality of perforation-sealing balls using an automated device as set forth in U.S. Pat. No. 4,132,243 to Kuus. Same-sized balls are used sealing perforations and are amenable feeding one by one from a stack of balls. The apparatus appears limited to same-sized balls and there is not positive identification whether a ball was successfully indexed from the stack for injection.

There remains a need for a safe, efficient and remotely operated apparatus and mechanism for introducing drop balls to a wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of a well undergoing stimulation operation using an embodiment of the invention connected to a top of a wellhead and a fanciful representation of downhole tools and zones along the wellbore;

FIG. 1B is a schematic view of a well undergoing stimulation operation using an embodiment of the invention connected to the wellbore through a fluid line and having a separate fluid pump connected thereto;

FIG. 1C is a schematic view of a well undergoing stimulation operation using an embodiment of the invention wherein the apparatus is fluidly connected to the stimulation fluid flow line through a bypass;

FIG. 2 is a side view of a wellhead illustrating typical fracturing fluid side entrances and insertion of a drop ball through the top of a wellhead;

FIG. 3A is a top, cross-sectional view of a ball magazine and actuator according to an embodiment of the invention, with the wellhead removed for clarity;

FIG. 3B is an end view of the ball magazine of FIG. 3A along section B-B illustrating a magazine alignment keyway formed therein;

FIGS. 4A-4D are top cross-sectional views of the ball magazine of FIG. 3, illustrating the loaded ball magazine and the sequential deployment of three drop balls, a first small ball, a second medium ball and a third large ball, respectively;

FIGS. 5A-5C are sequential longitudinal plan sectional views of an embodiment of the invention illustrating a system for indicating position of the magazine within the housing, more particularly

FIG. 5A illustrates a first position wherein no chambers within the magazine are aligned with the wellbore and an indicator rod engages a first indicator pin;

FIG. 5B illustrates a second position wherein a first chamber and ball are aligned with the wellbore and the indicator rod engages a second indicator pin, the first pin having been removed to permit movement of the magazine; and

FIG. 5C illustrates a subsequent position wherein a last chamber and ball are aligned with the wellbore and the indicator rod engages a final indicator pin; and

FIG. 6 is a side longitudinal sectional view according to FIG. 5A.

SUMMARY OF THE INVENTION

According to embodiments of the invention, a ball injecting apparatus can serially inject a first drop ball and subsequent drop balls into a wellbore, such as for actuating downhole tools. The apparatus comprises: a magazine housing having an axial bore formed therethrough and a transverse port, the transverse port being adapted for fluidly connecting to the wellbore; a magazine axially movable in the axial bore, the magazine having two or more transverse chambers spaced axially therealong, each chamber being adapted for receiving an individual drop ball therein; and an actuator for axially positioning the magazine within the axial bore between a loaded position where none of the two or more chambers are axially aligned with the transverse port, and an injection position where one selected chamber of the two or more chambers is moved into alignment with the transverse port wherein a drop ball for the selected chamber is injected from the selected chamber and through the transverse port to the wellbore. As suitable actuator includes a hydraulic ram which can be operated remotely connected by a piston rod to the magazine. A rod can extend from the magazine and through the magazine housing for indicating the relative position of the chambers and the transverse port. Sensors can complement the indicator.

The apparatus enables a system and methodology for injecting drop balls into a flow passage including systems for operations on wellbores. The ball injecting apparatus is provided. The first of the two or more of the chambers is loaded with a first drop ball loaded therein and each subsequent chamber having a subsequent drop ball loaded therein. The apparatus is mounted so that the transverse port is fluidly connected to the flow passage. The actuator is actuated to move the magazine in the magazine housing to axially align the first chamber with the transverse port for injecting the first drop ball from the first chamber and through the transverse port to the flow passage. As needed, one serially repeats the actuating step for each subsequent chamber for serially injecting each of the subsequent drop balls from the subsequent chambers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention are discussed herein in the context of the actuation of a series of packers within a wellbore for isolating subsequent zones within the formation for fracturing of the zones. A series of packers typically use a series of different sized balls for sequential blocking of adjacent packers. One of skill in the art however would appreciate that the invention is applicable to any operation requiring the dropping of one or more balls into the wellbore.

It has been known to drop a ball from surface through a tubular in a wellbore and into a seat of a downhole tool for blocking flow and permitting changes in pumped pressure to actuate downhole equipment such as movement of a sliding sleeve, opening and closing of a port, movement of a valves, fracturing of a frangible element, release of cementing wiper plugs, control of downhole packers, sealing perforations and the like. The diameter of the ball and the sequence of the release one or more drop balls into the wellbore is relevant to actuation of a series of packers for operations which can include as fracturing, acid stimulation and other stimulation procedures directed to zones of interest within the formation surrounding the wellbore.

In embodiments of the invention, a ball injecting apparatus 1 is fluidly connected to a wellbore 2 for positively introducing a specific ball into a fluid stream for injecting the ball into the wellbore.

In embodiments of the invention, as shown in FIGS. 1A-1C and 3A, flow passage P is fluidly connected to a wellbore 2 such as through a wellhead 3. To minimize the risk of ball hang-up, the flow passage P can be fluidly connected along a non-tortuous path such as to through a top of the wellhead or an angled port. A ball injecting apparatus 1 is fit to the flow passage P and generally comprises a ball magazine 4 loaded with one or more balls 8 and actuator 5 for positioning the magazine 4 for aligning a ball 8 with the flow passage P and assuring injection of the ball.

With reference to FIGS. 1A-1C, and in the context of fracturing or treating sequential zones within a formation accessed by the wellbore 2, the wellhead 3 is connected to pump trucks 6 through a fluid line 7 for supplying a fracturing or stimulation fluid to the wellbore 2. The wellhead 3 can be fit with a frac head or a wellhead isolation tool having a bore sufficiently large to permit the passage of the balls 8 therethrough. The pump trucks 6 are generally connected to a blender 9 and treatment fluid tanks 10 through which the components of the fracturing fluid, including sand or other proppant 11, are blended for delivery through the fluid lines 7 to the wellhead 3 and to the wellbore 2 connected thereto. The wellhead 3 forms the flow passage P to the wellbore 2.

As shown in the embodiment of FIG. 1A, the ball injecting apparatus 1 is connected to the flow passage P by directly mounting to the wellhead 3. Balls 8 can be injecting directly into the wellhead 3 by gravity or fluid which urges the balls 8 from the magazine 4 and into the flow passage P. In many instances, a flow of fluids F is introduced through flow passage P or other ports in the wellhead to the wellbore 2 therebelow. By injecting the ball 8 directly into the flow passage P to join the flow fluid F one avoids accidental lodging of the ball 8 in side ports or other cavities such as in some prior art T-configuration injection apparatus.

Alternatively, as shown in FIG. 1B, the flow of fluid F can flow through the ball injecting apparatus 1. The ball injecting apparatus 1 can be fluidly connected to the wellhead 3 intermediate a separate fluid supply line 14 and pump 15 for fluidly injecting balls 8 into the flow of fluids F being conducted in the wellbore 2. In an embodiment of the invention, frac fluid is introduced to the wellbore 3 through side ports 16 in a frac head 17 mounted below the fluid connection of the ball injecting apparatus 1. The ball injecting apparatus 1 and separate fluid supply line 14 are connected to the wellhead 3 at a top port 18 of the wellhead 2 which is substantially in-line with the wellbore 2. The ball injecting apparatus 1 and the flow passage P can be connected through known angled multi-ports (not detailed) of a frac head, typically angled in the range of 30 to 45 degrees.

Further, as shown in the embodiment of FIG. 1C, and particularly in the case of operations for injecting fluids containing no proppant, the ball injecting apparatus 1 may be fluidly connected to the wellhead 3 through a bypass 19 from a main treatment fluid supply line 20. Valves are provided to route fluids through the bypass 19 to propel the balls 8 from the magazine 4 and along the flow passage P to the wellhead 3.

As shown in the wellhead configuration of FIG. 2, where the ball 8 is introduced along a flow passage P which is generally in-line with wellbore 2, the ball 8 does not need to change direction and is reliably introduced into the flow of fluids F through the wellhead 3 for delivery down the wellbore.

Generally, as shown in FIGS. 3A and 3B, and in embodiments of the invention, the ball injecting apparatus 1 comprises a tubular magazine housing 30 having an axial bore 31 formed therein for receiving the magazine 4. The housing 30 is fit with a transverse port 37, generally transverse to the axial bore for forming a single point of egress for an injected ball 8 and becomes fluidly connected and contiguous with the flow passage P. The transverse port 37 is adapted for fluid connection with a bore 12 of the wellhead 3 (FIG. 1A) or intermediate a fluid line 14,20 (FIGS. 1B,1C), referred to collectively herein as the flow passage P. When connected intermediate a flow line 14,20, the transverse port is a flow-though port having fluid connections on opposing sides of the magazine housing 30. The magazine 4 comprises a piston-like linearly-extending body 4 b having two or more of chambers 32 for storing two or more drop balls 8, one ball per chamber. Each chamber 32 can receive, store and discharge an individual drop ball 8. Each chamber 32 is typically a transverse, substantially cylindrical passageway or bore through the body 4 b for forming entrance and exit openings 33,33. When a selected chamber 32 is axially and rotationally aligned with the transverse port 37, the chamber 32 and transverse port 37 are fluidly contiguous with the flow passage P. The chambers 32 and the apparatus 1 itself can be sized to accept a range of diameters of balls up to the largest ball required for the particular operation.

The bore 31 is sealed at opposing ends of the housing 34,35 so as to retain fluid pressure in the flow passage P. The magazine 4 can be removeably secured in the bore 31 of the magazine housing 30 using quick release unions 36,36 such as hammer union assemblies, that permit easy access to the magazine housing 30 to remove, load and replace a loaded magazine 4. Alternatively the magazine 4 may be secured within the magazine housing 30 using other releasable connections. The apparatus 1 is designed to American Petroleum Institute (API) standards for the particular design criteria including pressure and fluid characteristics. The magazine housing 30 is fluidly connected to the flow passage P for injecting the one or more balls 8 from the magazine 4.

Best shown in FIG. 6, in embodiments of the invention, the transverse port 37 forms a contiguous passage between the openings 33 of the ball chambers 32 and the flow passage P. In the case where the apparatus 1 is mounted intermediate a fluid flow line 14,20 (FIGS. 1B and 1C) connected to the flow passage P, the transverse port 37 is formed on opposing sides of the magazine housing 30. When one of the chambers' is axially aligned with the transverse port 37, the chamber 32 is fluidly connected to the flow passage P, for release of the ball 8 thereto. Where an axis CA of each of the two of more chambers 32 is parallel to the axis of each other chamber 32, mere axial positioning of the magazine 4 will align each chamber in turn with the transverse port 37. In the case where the apparatus 1 is connected directly to the wellhead 3 (FIG. 1A), the drop balls 8 can dropped out of the transverse port 37 by gravity and directly into the wellhead 3.

The magazine 4 is reciprocally actuated within the housing's bore 31 for manipulating the magazine 4 axially along the bore 31 so as to sequentially position, or align, each chamber 32 in-line with the transverse port 37 and flow passage P for deploying the drop balls 8 therein. The chambers 32 are axially spaced therealong. The chambers 32 can be evenly and axially spaced for ease of indexing the movement of the magazine 4.

The magazine 4 is actuated between an initial loaded position (FIGS. 3A,4A), where none of the chambers 32 are aligned with the transverse port 37, and an injection position (FIGS. 4B-4D), where one selected chamber 32 is moved into alignment with the transverse port 37. When aligned, a drop ball 8 for the selected chamber 32 is injected through the transverse port 37 along the flow passage P to the wellbore 2.

The magazine 4 is actuated reciprocally axially within the bore 31 by the actuator 5. The magazine 4 itself, and the actuation thereof, is insensitive to the size of the balls. Each chamber 32 can be sized for a particular-sized drop ball or similarly sized so as to receive and store one drop balls of a range of balls diameters without interference with the actuation and injection of drop balls therefrom. All chambers 32 can be sized to accommodate the largest diameter of the anticipated drop balls 8.

A suitable actuator 5 is a conventional double-acting hydraulic ram 40 having a piston 41 in a cylinder 42. The piston 41 is operatively connected to the magazine 4, such as through a piston rod 43. A piston rod seal or seals 48 are positioned between the magazine housing 30 and the piston rod 43 wherein the transverse port 37 and wellbore 2 are contained and further are isolated from the actuator 5. As shown in FIG. 3A, ports 44 are provided at opposing ends 45,46 of the cylinder 42 for connection to a control valve 47 (connection not illustrated) as understood by one of skill in the art, and which can be actuated remotely.

Illustrative of the apparatus 1 in operation, as shown in FIGS. 4A to 4D, and in an embodiment of the invention, the magazine 4 is preloaded with three drop balls 8 of different, increasing diameter in three similar-sized, corresponding chambers 32 of the magazine 4. Another embodiment capable of operation with up to five drop balls is illustrated in FIGS. 5A-6.

With reference to FIGS. 4A-4D, the loaded magazine 4 is inserted into the bore 31 of the magazine housing 30 and the connection 36 is secured. The balls 8 of increasing diameter can be differently and incrementally sized to actuate a series of downhole tools fit with corresponding ball seats. As shown in FIG. 4A, the preloaded magazine 4 is initially positioned into the magazine housing 30 with no chambers 32 aligned with the transverse port 37 or flow passage P so that no balls 8 are injected until actuated.

Subsequently, as shown in FIG. 4B, the actuator 5 is actuated to advance the magazine 4 in the magazine housing 30 to position a first chamber 32 a, housing a first, small diameter drop ball 8 a, into alignment with the flow passage P for injecting the ball 8 a therein. The ball 8 a can fall under gravity (into the sheet of FIG. 4C) or otherwise carried by a flow stream if intermediate the flow passage P. The first ball 8 a is typically sized to block a first downhole tool.

As shown in FIG. 4C, the actuator 5 is further actuated to advance the magazine 4 to position a second chamber 32 b, housing a medium diameter drop ball 8 b, into alignment with the flow passage P. Note the first chamber 32 a is now empty, the first ball 8 a having been previously injected into the flow passage P. The second ball 8 b is typically sized to block a second downhole tool, uphole from the first downhole tool.

As shown in FIG. 4D, the actuator 5 is further actuated to advance the magazine 4 to position a third chamber 32 c, housing a third and largest diameter drop ball 8 c, into alignment with the flow passage P. Note the first and second chambers 32 a,32 b are now empty and, in this embodiment, the first chamber 32 a happens to move axially beyond the flow passage P. The third ball 8 c is typically sized to block a third downhole tool, uphole from the second downhole tool.

As the magazine 4 is serially actuated, the body 4 b passes through the flow passage P and a distal end 49 enters a passage 50 at the distal end 34 of the bore 31 which accepts the axial length of the magazine 4. The distal end 49 of the magazine 4 rests inside the distal end 34 of the bore 31 and can be further supported thereby.

As shown in FIGS. 5A-6, additional chambers 32 for housing additional balls 8 can be implemented within an extended linear magazine 4 to operate a greater number of downhole tools. A length of the magazine housing 30, the magazine 4, the passage 50 and the stroke of the actuator 5 is adjusted accordingly.

In embodiments of the invention of FIGS. 3A-6, an indicator system 60 is provided for confirmation of alignment of a chamber 32 with the flow passage P and further for confirming which of the chambers 32 is aligned with the flow passage P so as to ensure a known drop ball 8 of known size is injected when required.

As shown in FIG. 3A the indicator 60 may comprise an electronic indicator 61 for indicating relative position of the magazine and transverse port 37. Such an indicator 60 could include devices between the housing and magazine or on the actuator 5. For example, a magnet 62 and pickup 63 could be arranged on a hydraulic ram 40 or alternatively a graded rod 64 (FIG. 3A) connected to the hydraulic cylinder 42. The indicator 60 precisely confirms the selected chamber 32 and drop ball 8 which is positioned for injection downstream.

As shown in FIGS. 5A-5C and 6, the indicator system 60 may comprise an indicator rod 65 extending from an end 66 of the magazine 4 and through the magazine housing 30 opposite the hydraulic ram 40. An indicator rod seal or seals 51 are positioned between the magazine housing 30 and the indicator rod 65 wherein the transverse port 37 and wellbore 2 are contained.

In an embodiment, the indicator rod 65 extends through an indicator housing 67 and includes an indicator disc 68 mounted thereto at a distal end 69. The indicator housing 67 is bored axially therealong with holes 70 at spaced intervals which correspond to the position of each of the chambers 32 in the magazine 4 when each chamber 32 is aligned with the flow passage P.

Indicator stops or pins 71 can be inserted into the holes 70 against which the indicator disc 68 engages or stops, indicating that a chamber 32 is aligned with the transverse port 37. First and subsequent indicator pins 71 can be sequentially or serially removed, enabling manual advancing the magazine 4 until the rod disk 68 engages each subsequent pin 71. U-shaped pins are illustrated using pairs of holes 70, for ease of handling, although straight pins, discs and slots or other removable stops could be used.

Alternatively, the indicator pins 71 may be shear pins. A slight but measurable increase in pressure at the actuator 5 would indicate to an operator that the disc 68 had engaged an indicator pin 71 and that a drop ball 8 had been aligned and dropped into the flow passage P. For releasing a subsequent drop ball 8, the magazine 4 would then be actuated under sufficient pressure to shear the indicator pin 71 and shift the magazine 4 axially until the indicator disc 68 engaged the next indicator pin 71.

In the embodiment of FIGS. 5A-5C, as opposed to that shown in FIG. 3A, the addition of the indicator rod system 60, through the indicator seal 51 at the opposite end 66 of the magazine housing 30 to the hydraulic ram 40, acts to balance the fluid force on the piston rod 43. Thus, lower forces are required to advance the piston 41 and magazine 4, reducing stress on the moving components. Further, only a small cylinder 42 is then required which acts to reduce the weight of the ball injecting apparatus 1.

Optionally, sophisticated hydraulic rams 40 could have built-in mechanical or electrical measurement systems effective to indicate when the chambers 32 have been aligned with the flow passage P.

With reference to FIGS. 3A, 3B, 4C and 5C, in embodiments of the invention, rotational alignment means 80 are provided for ensuring that the magazine 4, having two or more parallel and spaced chambers 32 formed therein, remains rotationally oriented during axial manipulation of the magazine 4 for aligning each of the chambers 32 in turn with the transverse port 37. While the magazine housing 30 and magazine can have a cross-sectional profile which resists rotation, such as a corresponding polygonal profile, pressure conditions of the wellbore 2 encourage selection of a generally cylindrical housing 30 and magazine 4. Accordingly, means are provided for preventing rotation of the magazine 6 relative to the magazine housing 30. One of skill in the art would appreciate that alignment of the magazine 4 within the magazine housing 30 may be accomplished in a number of different ways including the use of splines, key and keyway combinations, locking nuts and the like.

As shown in FIGS. 3A,3B and in an embodiment of the invention, the magazine 4 is splined to the magazine housing 30 for retaining proper alignment of the chambers 32 throughout the axial manipulation of the magazine 4. As shown, the spline may include a simple key 81 formed within the magazine housing 30 and keyway 82 formed in the magazine 4.

Alternately, in an embodiment as shown in FIGS. 5A-5C, the indicator rod housing 67 is formed having a spline 83 extending therealong and the rod disc 68 has a keyway 84 formed therein for preventing rotation of the indicator rod 65 within the rod housing 67 and the magazine 4 connected thereto. Further, the indicator rod 65 may be connected to the magazine 4 through a connector employing co-operating polygonal openings and rod end profiles for preventing rotation of the magazine 4 relative to the aligned indicator rod 65 and the magazine 4 attached thereto.

Example Wellbore Operations

With reference to FIGS. 1A and 4A-4D, a system and method for conducting operations on a wellbore 2 are provided. The wellbore 2 is fit with two of more downhole tools T1,T2,T3, such as packers spaced at intervals along the wellbore for isolation of a first zone and subsequent zones Z1,Z2,Z3. The system and methodology can implement an embodiment of the ball injecting apparatus 1 of the present invention.

With assistance of the embodiment illustrated in FIG. 1A, the ball injecting apparatus 1 is mounted with the transverse port 37 fluidly connected directly atop a stimulation multi-port wellhead 3. A flow F of stimulation fluids 7 can be provided to the wellhead 3 and the apparatus 1 can inject drop balls 8 into the flow path P for delivery down the wellbore 2. As is known by those of skill in the art, operations on the wellbore can include actuating a first packer T1 for blocking flow therebelow so that stimulation operations can be conducted on a zone Z1 uphole of that first packer. One or more subsequent packers T2,T3, . . . Tn are provided uphole of the first packer T1.

As shown in FIG. 4A, the magazine 4 of a hydraulic actuated ball injecting 1 is preloaded with three different sized drop balls 8 a,8 b,8 c of increasing diameter required for the stimulation operation. As the magazine 4 is incrementally inserted into the magazine housing 30 the drop balls 8 are loaded into the chambers 32 in the sequence in which they are to be injected. Once all the drop balls 8 are loaded, the magazine 4 is fully engaged within the housing bore 31 and the hammer union 36 or other appropriate connection is secured.

As shown in FIG. 4B, the actuator 5 is actuated for moving the magazine and axially aligning a first or selected chamber 32 a with the transverse port 37 for injecting the first drop ball 8 a into the flow path P. The first drop ball moves downhole, in the wellbore, passing each of the subsequent packers Tn . . . T3,T2 until it engages the corresponding, first packer T1 for actuating or blocking the wellbore at the first packer. The drop ball 8 a engages a ball seat for isolating the zone Z1, in the wellbore uphole of the first packer T1, from the wellbore therebelow.

Once stimulation for the zone Z1 above the first packer T1 is complete, a new zone is isolated uphole of the first packer. As shown in FIG. 4C, the actuator 5 is actuated again for axially aligning a second and subsequent selected chamber 32 b with the transverse port 37 for injecting the subsequent drop ball 8 b into the flow path P. The subsequent drop ball 8 b traverses the wellbore 2, passing each of the subsequent packers Tn . . . T3 until the ball engages and actuates the corresponding, second and subsequent packer T2. The drop ball 8 b engages a corresponding ball seat of the subsequent packer T2 for isolating zone Z2 uphole of the subsequent packer.

If there is a need and yet another subsequent packer, the actuator 5 can be actuated again for axially aligning yet another subsequent selected chamber 32 c with the transverse port 37 for injecting a third and subsequent drop ball 8 c for actuating the subsequent packer T3.

The system and method is serially repeated for each packer and corresponding drop ball provided. 

1. A ball injecting apparatus for injecting drop balls into a wellbore comprising: a magazine housing having an axial bore formed therethrough and a transverse port, the transverse port being adapted for fluidly connecting to the wellbore; a magazine axially movable in the axial bore, the magazine having two or more transverse chambers spaced axially therealong, each chamber being adapted for receiving an individual drop ball therein; and an actuator for axially positioning the magazine within the axial bore between a loaded position where none of the two or more chambers are axially aligned with the transverse port, and an injection position where one selected chamber of the two or more chambers is moved into alignment with the transverse port wherein a drop ball for the selected chamber is injected from the selected chamber and through the transverse port to the wellbore.
 2. The ball injecting apparatus of claim 1 wherein each chamber is a transverse, substantially cylindrical bore through the magazine which is parallel and axially spaced from each other chamber.
 3. The ball injecting apparatus of claim 2 wherein the magazine is rotationally constrained for maintaining rotational alignment of the selected chamber with the transverse port.
 4. The ball injecting apparatus of claim 3 further comprising rotational alignment means for rotationally aligning the magazine and the magazine housing.
 5. The ball injecting apparatus of claim 4 wherein the rotational alignment means is a co-operating key and keyway between the magazine housing and the magazine.
 6. The ball injecting apparatus of claim 4 wherein the rotational alignment means is a co-operating key and keyway on the actuator.
 7. The ball injecting apparatus of claim 1 further comprising: an indicator rod extending from an end of the magazine opposite to the actuator, the indicator rod extending axially through the housing; and an indicator seal between the housing and the indicator rod.
 8. The ball injecting apparatus of claim 1 further comprising an indicator for signaling the position of the selected chamber.
 9. The ball injecting apparatus of claim 8 wherein the indicator is an electronic sensor for sensing relative position of the magazine with respect to the housing.
 10. The ball injecting apparatus of claim 8 wherein the indicator comprises: an indicator rod extending from an end of the magazine opposite to the actuator, the indicator rod extending axially through the magazine housing; an indicator seal between the housing and the indicator rod; an indicator disc at a distal end of the indicator rod; an indicator housing extending about the indicator rod and fixed relative to the magazine housing; a plurality of holes bored through the housing each of which is axial spaced at intervals to correspond to the axial spacing of the two or more chambers in the magazine; and removable stop pins for positioning in the plurality of holes along the indicator housing and acting between the indicator disc and the indicator housing for engaging the indicator disc thereagainst for signaling when one of the one or more chambers is aligned with the transverse port.
 11. The ball injecting apparatus of claim 10 wherein the pins are shear pins acting between the indicator disc and the indicator housing, the actuator being actuatable to cause one of the shear pins to shear and permit movement of the magazine to a subsequent shear pin to axially align the selected chamber with the transverse port.
 12. The ball injecting apparatus of claim 1 wherein the two or more chambers are similarly sized.
 13. The ball injecting apparatus of claim 1 wherein each chamber is axially and equally spaced from each other chamber.
 14. The ball injecting apparatus of claim 1 wherein the actuator comprises a double-acting hydraulic ram having a piston in a cylinder, the piston being operatively connected to the magazine.
 15. The ball injecting apparatus of claim 14 wherein the piston is connected to magazine by a piston rod.
 16. The ball injecting apparatus of claim 15 further comprising a piston rod seal between the magazine housing and the piston rod wherein the wellbore is isolated from the actuator.
 17. A method for injecting drop balls into a flow passage comprising: providing a ball injecting apparatus having a magazine housing having an axial bore formed therethrough and a transverse port, the transverse port being adapted for fluidly connecting to the wellbore; a magazine axially movable in the axial bore, the magazine having two or more transverse chambers spaced axially therealong, a first of the two or more of the chambers having a first drop ball loaded therein and each subsequent chamber having a subsequent drop ball loaded therein; and an actuator for axially positioning the magazine within the axial bore between a loaded position where none of the two or more chambers are axially aligned with the transverse port, and an injection position where one selected chamber of the two or more chambers is moved into alignment with the transverse port; mounting the ball injecting apparatus so that the transverse port is fluidly connected to the flow passage; actuating the actuator to move the magazine in the magazine housing to axially align the first chamber with the transverse port for injecting the first drop ball from the first chamber and through the transverse port to the flow passage; and serially repeating the actuating step for each subsequent chamber for serially injecting each of the subsequent drop balls from the subsequent chambers.
 18. The method of claim 17 wherein the mounting step comprising mounting the ball injecting apparatus to a top of a wellbore for forming the flow passage extending downward from the transverse port to the wellbore, wherein the selected ball is injected to the flow passage by gravity.
 19. The method of claim 17 wherein the mounting step comprises mounting the ball injecting apparatus intermediate a fluid flow line connected to the wellbore for forming the flow passage through transverse port of the ball injecting apparatus, wherein the selected ball is injected to the flow passage by fluid passing through the fluid flow line and the transverse port and to the wellbore.
 20. A system for injecting one or more balls into a wellbore for actuating a series of downhole tools comprising: a ball injecting apparatus having a magazine housing having an axial bore formed therethrough and a transverse port, the transverse port being adapted for fluidly connecting to the wellbore; a magazine axially movable in the axial bore, the magazine having two or more transverse chambers spaced axially therealong, a first of the two or more of the chambers having a first drop ball loaded therein and each subsequent chamber having a subsequent drop ball loaded therein; and an actuator for axially positioning the magazine within the axial bore between a loaded position where none of the two or more chambers are axially aligned with the transverse port, and an injection position where one selected chamber of the two or more chambers is moved into alignment with the transverse port; two or more downhole tools spaced at intervals along the wellbore, the two or more downhole tools comprising a first downhole tool actuable upon receipt of the first drop ball and each subsequent downhole tool actuable upon receipt of each subsequent drop ball; wherein when the actuator is actuated to move the magazine in the magazine housing to axially align the first chamber with the transverse port, the first drop ball is injected from the first chamber and through the transverse port to the wellbore for actuating the first downhole tool; and serially actuating the actuator for each subsequent chamber for serially injecting each of the subsequent drop balls from the subsequent chambers to serially actuate each of the subsequent downhole tools.
 21. The system of claim 20 wherein the two of more downhole tools are a first and subsequent packers for isolating a first zone and subsequent zones along the wellbore and the first packer is actuable upon receipt of the first drop ball for blocking the wellbore below the packer, and each subsequent packer is actuable upon receipt of the subsequent drop ball for blocking the wellbore below the subsequent packer; the subsequent drop ball has a diameter greater than the first drop ball and each subsequent ball has a diameter greater than an immediately preceding subsequent drop ball wherein each of the drop balls does not actuate the subsequent packer.
 22. The method of claim 21 further comprising: a wellhead fluidly connected to the wellbore, wherein the ball injecting apparatus is mounted to a top of the wellhead for forming a flow passage extending downward from the transverse port to the wellbore, wherein the selected ball is injected to the flow passage by gravity.
 23. The method of claim 21 further comprising: a wellhead fluidly connected to the wellbore; and a fluid flow line for flowing fluid to the wellhead, wherein the ball injecting apparatus is mounted intermediate the fluid flow line forming a flow passage through transverse port of the ball injecting apparatus and to the wellbore, wherein the selected ball is injected to the flow passage by fluid passing through the fluid flow line and the transverse port and to the wellbore.
 24. The system of claim 23 wherein the wellhead further comprises a wellhead isolation tool having a bore of sufficient size to accept the first and subsequent drop balls. 